basil said:
It's possible to spur from the upstairs lighting........
Indeed, but I presume that he wants to fit a socket and, whilst there's no practical reason not to do this, as long as you consider the supply that will be available, it is probably only a matter of time before somebody plugs two kettles in and pops the lights. It would, of course, also contravene the wiring regs, but, then, so does almost everything anyway..
If it's only for a few watts and it was under my control then I would probably do it. One does have to consider the residual current device, however, as lighting circuits may be excluded from being covered by this, but any sockets should be, really.